IQ

A few days ago my brother bet me $10 that his IQ was ten points higher than mine. We have a running joke in my family never to bet me on anything, because I NEVER bet unless I am SURE that I will win. So I was surprised that when I agreed to this bet, he did not back down.
We haven't taken this test yet, and I've never taken a real IQ test before, but his confidence is based on results he had several years ago when he took the test in high school. However, even if he WAS ten points higher than me at some point, I doubt he still is today... he's been smoking pot/drinking for the last 6 or 7 years and I haven't.
His theory is that IQ tests are based on logical reasoning, and since I am horrible at math, I am therefore illogical (hmmm...). However. My thinking is that, even if his IQ is higher than mine, there is no way it can be ten points higher than mine-- that is a significant difference. (His original bet was thirty points, which is stupid in and of itself... because if there was that much of a difference in our levels of intelligence we would have trouble communicating and understanding each other. So that in and of itself is a red flag as to his own level of logical reasoning...)
Besides-- IQ tests aren't math tests. And we had the same exact score on our SATs, just that our math and verbal results were switched.
So, essentially, there is no logical reason for him to believe he is significantly smarter than me, and I'm looking forward to my $10.